Question

The heart of a man pumps $5$ litres of blood through the arteries per minute at a pressure of $150 \,mm$ of mercury. If the density of mercury be $13.6 \times 10^3$ $kg/m^3$ and $g$ = $10\, m/s^2$ then the power

• A. 3
• B. 1.5
• C. 1.7
• D. 2.35

Answer 1

Answer: (C)

1.7

Answer 2

Here , Volume of blood pumped by man's heart, V=5 litres=$5 \times 10^{-3}m^3 \, \, \, \, \,$ ($\because \, 1$ litre $=10^{-3} m^{3}$) Time in which this volume of blood pumps, t = 1 min = 60 s Pressure at which the blood pumps , P = 150 mm of Hg = 0.15 m of Hg =(0.15 m) (13.6 $\times 10^{3}\,kg/m^3$)(10 m/s$^2$) $(\because \, P=h\rho g)$ =20.4 $\times \, 10^3 \, N/m^2$ $\therefore \, \, \,$ Power of the heart =$\frac{PV}{t}$ $=\frac{(20.4 \times 10^3 N/m^2)(5 \times 10^{-3}m^3)}{60 s}=1.70 W$